2,802 research outputs found
Scattering Phases and Density of States for Exterior Domain
For a bounded open domain with connected complement and
piecewise smooth boundary, we consider the Dirichlet Laplacian -\DO on
and the S-matrix on the complement . Using the restriction
of to the boundary of , we establish that
is trace class when is negative and
give bounds on the energy dependence of this difference. This allows for
precise bounds on the total scattering phase, the definition of a
-function, and a Krein spectral formula, which improve similar results
found in the literature.Comment: 15 pages, Postscript, A
Controllability for chains of dynamical scatterers
In this paper, we consider a class of mechanical models which consists of a
linear chain of identical chaotic cells, each of which has two small lateral
holes and contains a rotating disk at its center. Particles are injected at
characteristic temperatures and rates from stochastic heat baths located at
both ends of the chain. Once in the system, the particles move freely within
the cells and will experience elastic collisions with the outer boundary of the
cells as well as with the disks. They do not interact with each other but can
transfer energy from one to another through collisions with the disks. The
state of the system is defined by the positions and velocities of the particles
and by the angular positions and angular velocities of the disks. We show that
each model in this class is controllable with respect to the baths, i.e. we
prove that the action of the baths can drive the system from any state to any
other state in a finite time. As a consequence, one obtains the existence of at
most one regular invariant measure characterizing its states (out of
equilibrium)
Method of constructing exactly solvable chaos
We present a new systematic method of constructing rational mappings as
ergordic transformations with nonuniform invariant measures on the unit
interval [0,1]. As a result, we obtain a two-parameter family of rational
mappings that have a special property in that their invariant measures can be
explicitly written in terms of algebraic functions of parameters and a
dynamical variable. Furthermore, it is shown here that this family is the most
generalized class of rational mappings possessing the property of exactly
solvable chaos on the unit interval, including the Ulam=Neumann map y=4x(1-x).
Based on the present method, we can produce a series of rational mappings
resembling the asymmetric shape of the experimentally obtained first return
maps of the Beloussof-Zhabotinski chemical reaction, and we can match some
rational functions with other experimentally obtained first return maps in a
systematic manner.Comment: 12 pages, 2 figures, REVTEX. Title was changed. Generalized Chebyshev
maps including the precise form of two-parameter generalized cubic maps were
added. Accepted for publication in Phys. Rev. E(1997
POOL File Catalog, Collection and Metadata Components
The POOL project is the common persistency framework for the LHC experiments
to store petabytes of experiment data and metadata in a distributed and grid
enabled way. POOL is a hybrid event store consisting of a data streaming layer
and a relational layer. This paper describes the design of file catalog,
collection and metadata components which are not part of the data streaming
layer of POOL and outlines how POOL aims to provide transparent and efficient
data access for a wide range of environments and use cases - ranging from a
large production site down to a single disconnected laptops. The file catalog
is the central POOL component translating logical data references to physical
data files in a grid environment. POOL collections with their associated
metadata provide an abstract way of accessing experiment data via their logical
grouping into sets of related data objects.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, 1 eps figure, PSN MOKT00
Covariant Lyapunov vectors for rigid disk systems
We carry out extensive computer simulations to study the Lyapunov instability
of a two-dimensional hard disk system in a rectangular box with periodic
boundary conditions. The system is large enough to allow the formation of
Lyapunov modes parallel to the x axis of the box. The Oseledec splitting into
covariant subspaces of the tangent space is considered by computing the full
set of covariant perturbation vectors co-moving with the flow in tangent-space.
These vectors are shown to be transversal, but generally not orthogonal to each
other. Only the angle between covariant vectors associated with immediate
adjacent Lyapunov exponents in the Lyapunov spectrum may become small, but the
probability of this angle to vanish approaches zero. The stable and unstable
manifolds are transverse to each other and the system is hyperbolic.Comment: 23 pages, 17 figures; Chemical Physics, in press, June 2010. Chem.
Phys. (2010): cited as: H. Bosetti, H.A. Posch, Chem. Phys. (2010),
doi:10.1016/j.chemphys.2010.06.01
The cytoplasmic poly(A) polymerases GLD-2 and GLD-4 promote general gene expression via distinct mechanisms
Post-transcriptional gene regulation mechanisms decide on cellular mRNA activities. Essential gatekeepers of post-transcriptional mRNA regulation are broadly conserved mRNA-modifying enzymes, such as cytoplasmic poly(A) polymerases (cytoPAPs). Although these non-canonical nucleotidyltransferases efficiently elongate mRNA poly(A) tails in artificial tethering assays, we still know little about their global impact on poly(A) metabolism and their individual molecular roles in promoting protein production in organisms. Here, we use the animal model Caenorhabditis elegans to investigate the global mechanisms of two germline-enriched cytoPAPs, GLD-2 and GLD-4, by combining polysome profiling with RNA sequencing. Our analyses suggest that GLD-2 activity mediates mRNA stability of many translationally repressed mRNAs. This correlates with a general shortening of long poly(A) tails in gld-2-compromised animals, suggesting that most if not all targets are stabilized via robust GLD-2-mediated polyadenylation. By contrast, only mild polyadenylation defects are found in gld-4-compromised animals and few mRNAs change in abundance. Interestingly, we detect a reduced number of polysomes in gld-4 mutants and GLD-4 protein co-sediments with polysomes, which together suggest that GLD-4 might stimulate or maintain translation directly. Our combined data show that distinct cytoPAPs employ different RNA-regulatory mechanisms to promote gene expression, offering new insights into translational activation of mRNAs
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